Vessel and method for treating contaminated water

ABSTRACT

A method for removing immiscible fluid from contaminated water includes at least one chamber; an injection line in fluid communication with an inlet of the one chamber; bubble generation means in fluid communication with the injection line for injecting gas bubbles into the injection line and allowing mixing in the injection line of the gas bubbles and the contaminated water to form an inlet fluid; an inlet weir within the chamber adjacent the inlet; an immiscible fluid weir within the chamber; a trough for collecting the immiscible fluid and allowing the immiscible fluid to flow out of the at least one chamber through an immiscible fluid outlet; and a cleaned water outlet generally at the bottom of the chamber.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional patent application of U.S. patentapplication Ser. No. 11/284,012 filed Nov. 22, 2005.

FIELD

The present invention relates to water treatment vessels and methods ofuse, and more particularly to vessels used in treating watercontaminated with immiscible fluids such as oil and bitumen.

BACKGROUND

This section provides background information related to the presentdisclosure which is not necessarily prior art.

Water produced by various commercial and industrial processes is oftencontaminated, particularly by oil and solid materials as is the case inthe downstream petroleum industry, or may disadvantageously containdifferent component phases. Prior to discharge or re-use of thisproduced water, some form of treatment is generally required (either tore-use the produced water in subsequent process stages, or due togovernmental regulation of discharge quality).

In the context of the petroleum industry, produced water can containsmall oil droplets held in suspension. Various methods and apparatushave been proposed to enable the separation of the oil from the producedwater, usually employing some form of flotation system.

One separation technology employed in the petroleum industry is the useof API and gravity separation tanks, such as a “skim tank”. Thistechnology is relatively simple and inexpensive, depending on thedifferent densities of oil and water to enable gravity separation.Contaminated water is held in a vessel for a predetermined period oftime, during which time the oil separates from the water and rises andcollects at the vessel surface, allowing for skimming off of the oil.Parameters such as retention time, oil properties and inlet streamcharacteristics can be controlled to enhance separation, and tankdimensions are also of crucial importance. While such separators can bequite effective in removing larger oil droplets, however, they aregenerally ineffective in removing oil droplets of less than 50 microns(even if chemical treatments are added) and require substantialretention times.

Another well-known technology is the corrugated plate interceptor (CPI).In CPI vessels, corrugated plates are used to amplify the densitydifferences by providing an inclined plate with a longer fluid travelpath. With an inclined plate, individual oil droplets are presented witha shorter travel path to reach adjacent oil droplets, creating largercoalesced oil droplets which rise more quickly to the fluid surface.This allows for vessels with a much smaller footprint than withtraditional gravity separation vessels, but it has the same limitationof being generally ineffective in removing oil droplets of less than 50microns. In addition, chemical usage is increased and CPI vesselsusually cope poorly with flow surges.

Induced gas flotation (IGF) vessels are also known in the industry,where gas is induced into the contaminated water (by means usuallyincluding eductors, sparging tubes and paddles) to more rapidly floatthe oil droplets out of the produced water. The oily froth is thenskimmed off, sometimes by a baffle system. While IGF is one of the mostprevalent technologies presently in use, it is still limited in terms ofthe oil droplet size that can be removed, and chemical treatment istherefore required. Also, the technology generally cannot be efficientlyemployed in retrofit situations.

Induced static flotation (ISF) technology is also known in the industry.This is another induced gas system, although it uses a different methodof gas bubble generation than with IGF methods. In IGF systems, thebubbles are generated by mechanical means, while in ISF systems thebubbles are created by hydraulic methods. ISF vessels are usuallyseparated into chambers, with gas introduction in each of the chambers,and ISF methods can be employed with a pressurized vessel. Onelimitation of ISF systems is that they have difficulty coping with oilconcentrations above 300 ppm. In addition, such systems do notadequately address flow rate fluctuations, and retrofit capability isgenerally absent.

Hydrocyclones have also been used in the petroleum industry to treatcontaminated produced water. These are conical tubes, and contaminatedwater is tangentially introduced into the upper end. The fluid spinsaround the tube, creating a centrifugal force that forces oil upwardsand out of the tube while allowing the cleaned water to drain downwards.However, hydrocyclones are used in groupings based on flow rate, and thesystem cannot cope well with flow rate changes and the resultant fluidvelocity shift. Also, there is a substantial pressure drop across thesystem, and a separate system is required to remove any solids in theproduced water. Solids blockages can also be a problem, and the solidsthemselves can result in significant wear of the tube interior.

Finally, centrifuges have been used to treat produced water, withspinning forcing a separation of the oil and water. Unlike thehydrocyclones, centrifuges use moving parts to generate the spinningmotion. While very effective in removing solids and enabling oil/waterseparation, the low flow rates and susceptibility to wear areproblematic.

What is needed, therefore, is a water treatment vessel and method thatdoes not require a substantial retention period, that can remove oildroplets less than 50 microns in diameter, and that can handle flow ratefluctuations. In addition, it would be advantageous to provide a vesselwith a relatively small footprint, and the ability to handle solids aswell as oil concentrations of greater than 300 ppm. Reducing the needfor moving parts and chemical treatments, while allowing for retrofit ofexisting tanks, would also be desirable.

SUMMARY

This section provides a general summary of the disclosure, and is not acomprehensive disclosure of its full scope or all of its features.

According to a first aspect of the present invention there is provided awater treatment vessel for removing immiscible fluid from contaminatedwater to produce cleaned water, the vessel comprising: at least onechamber; an injection line in fluid communication with an inlet of theat least one chamber, the injection line for containing and transmittingthe contaminated water from a source; bubble generation means in fluidcommunication with the injection line for injecting gas bubbles into theinjection line and allowing mixing in the injection line of the gasbubbles and the contaminated water to form an inlet fluid; an inlet weirsupported within the at least one chamber by first mounting meansadjacent the inlet; an immiscible fluid weir supported within the atleast one chamber by second mounting means, spaced from the inlet weir;a trough for collecting the immiscible fluid and allowing the immisciblefluid to flow out of the at least one chamber through an immisciblefluid outlet; and a cleaned water outlet generally at the bottom of theat least one chamber; wherein when the inlet fluid is injected into theat least one chamber, it passes through the inlet and over the inletweir, the cleaned water flows downwardly toward the cleaned wateroutlet, and a remaining mixture of the immiscible fluid and the gasbubbles floats through the chamber to pass over the immiscible fluidweir and down the trough to the immiscible fluid outlet.

In exemplary embodiments of water treatment vessels according to thepresent invention, the immiscible fluid is oil or bitumen, and the watertreatment vessel is substantially cylindrical, although it may also berectangular, as discussed below. The water treatment vessel may bedisposable in either a horizontal or vertical orientation. When disposedin a horizontal orientation, the first mounting means comprises a directmounting of the inlet weir on a first interior surface of the at leastone chamber adjacent the inlet, and the second mounting means comprisesa direct mounting of the immiscible fluid weir on a second interiorsurface of the at least one chamber spaced from the inlet weir. Whendisposed in a vertical orientation, the inlet weir is centrally disposedwithin the at least one chamber, the immiscible fluid weir iscircumferentially disposed about the inner surface of the at least onechamber, and the immiscible fluid weir is spaced from and disposedgenerally above the inlet weir.

The water treatment vessel preferably comprises at least two chambers(most preferably substantially of equal volume), the at least twochambers in fluid communication by means of at least one connectingpipe, the at least one connecting pipe for allowing the cleaned water topass from the bottom of a first of the at least two chambers to a pointadjacent the inlet weir of an adjacent second of the at least twochambers, the cleaned water outlet generally at the bottom of a last ofthe at least two chambers. The vessel also preferably comprises gasbubble injection means in fluid communication with the at least oneconnecting pipe for selectively injecting gas bubbles at a location inthe at least one connecting pipe spaced from the inlet weir of theadjacent second of the at least two chambers, the gas bubbles preferablybeing microbubbles (most preferably each being less than 50 microns indiameter) composed of a gas selected from the group consisting of air,hydrocarbon gas, and nitrogen. The two adjacent chambers of the at leasttwo chambers are preferably separated by a substantially vertical wallfor separating fluids contained in each of the two adjacent chambers,with the substantially vertical wall extending from a lower innersurface of the water treatment vessel toward but spaced from an upperinner surface of the water treatment vessel, for containing fluids ineach of the two adjacent chambers while allowing gas exchange betweenthe two adjacent chambers. The at least one connecting pipe preferablypasses through the substantially vertical wall and enables fluidcommunication between the two adjacent chambers.

The inlet weir preferably comprises a base portion and a wall portion,the wall portion generally angled upwardly and outwardly from the baseportion, for directing the inlet fluid upwardly and away from the inlet,and the immiscible fluid weir preferably comprises a base portion and awall portion, the wall portion generally angled upwardly and outwardlyfrom the base portion, for receiving the remaining mixture of theimmiscible fluid and the gas bubbles.

The vessel also preferably comprises nozzle means on the inlet, andrecycle flow means for redirecting at least a portion of the cleanedwater from the cleaned water outlet to the bubble generation means (mostpreferably, the recycle flow means are for directing approximately halfof the cleaned water from the cleaned water outlet to the bubblegeneration means). The vessel further preferably comprises flow controlmeans on the cleaned water outlet to allow a steady state, formaintaining volume of fluid exiting the cleaned water outletsubstantially equal to volume of the inlet fluid entering the watertreatment vessel, and at least one globe valve for controlling gasbubble injection into the injection line.

The vessel preferably comprises weir adjustment means to enable heightadjustment of the immiscible fluid weir to minimize clean water loss, aswell as at least one observation port in the at least one chamber toenable height adjustment of the immiscible fluid weir. The weiradjustment means preferably comprise a threaded spindle extendingthrough the water treatment vessel and sealed by a packing gland,rotation of the spindle causing height adjustment of the immisciblefluid weir. The immiscible fluid weir is preferably composed ofpolyvinylidene fluoride. The water treatment vessel is preferablyprovided with an aperture adjacent the immiscible fluid weir and anozzle fitting housed within the aperture, the at least one observationport comprising a tempered glass viewing pane disposed between thenozzle fitting and a retention member, enabling visual inspection of theimmiscible fluid weir. The vessel preferably further comprisesobservation port clearing means, which most preferably comprise aconduit for selectively injecting gas or water into the nozzle fitting.

The trough may be provided with at least one heating coil to aid in flowof the immiscible fluid therealong, and the immiscible fluid outlet ispreferably in fluid communication with an immiscible fluid retentiontank adjacent the water treatment vessel.

In some exemplary embodiments where the water treatment vessel ishorizontally disposed, the vessel comprises five chambers in series,each chamber in fluid communication with adjacent chambers by means ofat least one connecting pipe, the at least one connecting pipe forallowing the cleaned water to pass from the bottom of one of the firstfour chambers to a point adjacent the inlet weir of an adjacent one ofthe last four chambers, the cleaned water outlet generally at the bottomof a last of the five chambers. The at least one connecting pipe ispreferably sized to minimize pressure drop across the chambers of thewater treatment vessel. The trough preferably runs substantially alongthe length of the water treatment vessel and is sloped to encourage flowof the immiscible fluid toward the immiscible fluid outlet, with theimmiscible fluid weir being disposed on the second interior surfacesubstantially opposite from and generally above the inlet weir.

In exemplary embodiments where the water treatment vessel is verticallydisposed, the inlet weir preferably comprises a base portion and aperipheral wall portion, the peripheral wall portion generally angledupwardly and outwardly from the base portion, for directing the inletfluid upwardly and away from the inlet, the injection line extendingacross the at least one chamber to enter the inlet weir. The immisciblefluid weir preferably comprises a wall portion, the second mountingmeans comprising the wall portion being directly mounted on an interiorsurface of the water treatment vessel and generally angled upwardly andinwardly from the interior surface, and the first mounting meanscomprising the inlet weir being supported by the injection line. Thefirst mounting means most preferably comprise the inlet weir beingsupported by at least one rib projecting from an inner surface of thewater treatment vessel.

The water treatment vessel may be a pressure vessel, where someoneskilled in the art would recognize the utility of such in a givencontext.

According to a second aspect of the present invention there is provideda method for removing immiscible fluid from contaminated water from asource, the method comprising the steps of:

(a) providing a water treatment vessel comprising at least one chamber,an inlet weir supported within the at least one chamber by firstmounting means, and an immiscible fluid weir supported within the atleast one chamber by second mounting means, spaced from the inlet weir;

(b) transmitting the contaminated water from the source toward the atleast one chamber by means of an injection line;

(c) providing bubble generation means for generating bubbles;

(d) generating and injecting the bubbles into the injection line;

(e) allowing the bubbles and contaminated water to mix in the injectionline to form an inlet fluid;

(f) injecting the inlet fluid into the at least one chamber at an inletadjacent the inlet weir;

(g) allowing the inlet fluid to pass over the inlet weir;

(h) allowing cleaned water and a remaining mixture of immiscible fluidand gas bubbles to separate from each other;

(i) allowing the cleaned water to flow downwardly by gravity to acleaned water outlet;

(j) draining off the cleaned water through the cleaned water outlet;

(k) allowing the remaining mixture of immiscible fluid and gas bubblesto float across the at least one chamber and over the immiscible fluidweir; and

(l) allowing the immiscible fluid to collect in a trough within the atleast one chamber and flow out an immiscible fluid outlet.

In exemplary embodiments of methods according to the present invention,the method further comprises a step after step (a) but before step (b)of providing the water treatment vessel with immiscible fluid weirheight adjustment means; and a step before step (k) of adjusting theimmiscible fluid weir height adjustment means to minimize cleaned waterloss over the immiscible fluid weir. Preferred methods then preferablyfurther comprise a step after step (a) but before step (b) of providingthe water treatment vessel with at least one observation port; and astep before step (k) of observing fluid level in the at least onechamber by means of the at least one observation port, to enableadjusting the immiscible fluid weir height adjustment means to minimizecleaned water loss over the immiscible fluid weir. Where at least oneobservation is provided, the method preferably further comprises a stepafter step (a) but before step (b) of providing the water treatmentvessel with observation port clearing means; and a step of injecting gasor water into the observation port to clear the observation port of anybuild-up.

In methods wherein the water treatment vessel is provided with at leasttwo chambers, the at least two chambers in fluid communication by meansof at least one connecting pipe, the method preferably further comprisesthe step after step (i) of allowing the cleaned water to pass from thebottom of a first of the at least two chambers to a point adjacent theinlet weir of an adjacent second of the at least two chambers by meansof the at least one connecting pipe. The bubble generation meanspreferably generate microbubbles, which are preferably composed of a gasselected from the group consisting of air, hydrocarbon gas, andnitrogen.

In exemplary methods, the method preferably comprises a step after step(j) of redirecting at least a portion of the cleaned water from thecleaned water outlet to the bubble generation means. Most preferably,approximately half of the cleaned water from the cleaned water outlet isredirected to the bubble generation means.

In some preferred embodiments, the method further comprises a step ofselectively injecting gas bubbles at a location in the at least oneconnecting pipe spaced from the inlet weir of the adjacent second of theat least two chambers. Most preferably, the method preferably furthercomprises a step of withholding gas bubble injection in the at least oneconnecting pipe leading into a last of the at least two chambers,thereby forming a calming zone.

In exemplary embodiments of methods according to the present invention,the method preferably comprises a step of providing the water treatmentvessel with flow control means on the cleaned water outlet; and a stepof using the flow control means to maintain volume of fluid exiting thecleaned water outlet substantially equal to volume of the inlet fluidentering the water treatment vessel, allowing for a steady state withinthe water treatment vessel. Preferred methods may further comprise: astep of disposing the water treatment vessel in a vertical orientation;a step of centrally disposing the inlet weir within the at least onechamber; and a step of circumferentially disposing the immiscible fluidweir about the inner surface of the at least one chamber, the immisciblefluid weir being spaced from and disposed generally above the inletweir. In some preferred embodiments, the method further comprises a stepafter step (l) of collecting the immiscible fluid in an immiscible fluidretention tank.

According to a third aspect of the present invention there is provided awater treatment vessel for removing immiscible fluid from contaminatedwater to produce cleaned water, the vessel disposable in a horizontalorientation and comprising:

five chambers in series, each chamber in fluid communication withadjacent chambers by means of a connecting pipe having an inlet openinginto a second of two adjacent chambers;

an injection line in fluid communication with an inlet of a first of thefive chambers, the injection line for containing and transmitting thecontaminated water from a source;

bubble generation means in fluid communication with the injection linefor injecting gas microbubbles into the injection line and allowingmixing in the injection line of the gas microbubbles and thecontaminated water to form an inlet fluid;

an inlet weir supported within each of the five chambers by a directmounting on a first interior surface of the chamber adjacent the inletof each chamber;

an immiscible fluid weir supported within each of the chambers by adirect mounting on a second interior surface of the chamber, spaced fromthe inlet weir;

a trough in communication with the immiscible fluid weir of each of thechambers for collecting the immiscible fluid and allowing the immisciblefluid to flow out of the chambers through an immiscible fluid outlet;and

a cleaned water outlet generally at the bottom of a last of the fivechambers;

wherein when the inlet fluid is injected into the first of the fivechambers, the inlet fluid passes over the inlet weir, the cleaned waterflows downwardly toward the bottom of the first of the five chambers andthrough the connecting pipe to a next adjacent chamber, the cleanedwater flows sequentially through each of the chambers, and the cleanedwater finally flows through the cleaned water outlet; and

wherein a remaining mixture of the immiscible fluid and the gasmicrobubbles floats through each of the chambers to pass over theimmiscible fluid weir and down the trough to the immiscible fluidoutlet.

According to a fourth aspect of the present invention there is provideda water treatment vessel for removing immiscible fluid from contaminatedwater to produce cleaned water, the vessel disposable in a verticalorientation and comprising:

a chamber;

an injection line in fluid communication with an inlet of the chamber,the injection line for containing and transmitting the contaminatedwater from a source;

bubble generation means in fluid communication with the injection linefor injecting gas microbubbles into the injection line and allowingmixing in the injection line of the gas microbubbles and thecontaminated water to form an inlet fluid;

an inlet weir centrally disposed and supported within the chamber byfirst mounting means adjacent the inlet of the chamber;

an immiscible fluid weir circumferentially disposed about an innersurface of the chamber, spaced from and disposed generally above theinlet weir;

a trough in communication with the immiscible fluid weir for collectingthe immiscible fluid and allowing the immiscible fluid to flow out ofthe chamber through an immiscible fluid outlet; and

a cleaned water outlet generally at the bottom of the chamber;

wherein when the inlet fluid is injected into the chamber, the inletfluid passes over the inlet weir, the cleaned water flows downwardlytoward the bottom of the chamber and through the cleaned water outlet;and

wherein a remaining mixture of the immiscible fluid and the gasmicrobubbles floats through the chamber to pass over the immisciblefluid weir and down the trough to the immiscible fluid outlet.

Vessels and methods according to the present invention can be used inconjunction with some known microbubble generation technologies. Forexample, Canadian Patent Application No. 2,460,123, assigned to theassignee of the present application, teaches an apparatus and method forproducing microbubbles in liquids, for use in treating contaminatedliquids. A vertical pipe receives a liquid-gas mixture having gasbubbles of relatively large diameter, and a series of horizontalapertures permit the pipe to expel the mixture radially outwardly fromthe pipe. In a refinement of the invention, a specific relationship isspecified between the exit area of the apertures and the interiorcross-sectional area of the pipe, in order to most suitably convert thegas bubbles in the mixture to microbubbles of a desired small size whenexpelled under pressure from the pipe. A method of converting gasbubbles in the mixture to gas microbubbles, and for exposing such gasmicrobubbles to material entrained in the mixture so as to permit thegas microbubbles to physically or chemically react with the materials,is further disclosed.

Water treatment vessels and methods according to the present inventioncan therefore provide numerous advantages over the prior art, includinga shorter lead time than is the case with alternative technologies onthe market, and the elimination of mechanical oil skimmingapparatus/steps. In addition, the microbubble generation mechanism isexternal to the chamber(s), and there are no diffusers or eductorswithin the water treatment sections of the vessel where it can bedifficult to clean and maintain components. A high degree of controlover gas rates/ratios and bubble size is also possible, at a loweroperating cost; vessels according to the present invention use noeductors, with the result that there is no pressure drop required,thereby saving significant operation costs when compared to knownvessels. The use of eductors requires a fairly fixed motive flow acrossthe vessel for operation, with little flexibility to allow an increaseor decrease in gas ratios and no control over bubble size; using avessel according to the present invention allows for operator controlover gas flow rates and bubble size by valve adjustment at the pump.

The ability to make use of microbubble technology allows for smallerbubble size than with some known vessel technologies, resulting inhigher separation efficiency, lower recirculation rates than otherinduced gas systems, removal of emulsified oil, and reduction (orelimination) of the need for additional chemicals to assist separation.

Accordingly, the present invention seeks to provide a water treatmentvessel and method that requires a minimal retention period, removes oildroplets less than 50 microns in diameter, and can handle solids, flowrate fluctuations, and oil concentrations of greater than 300 ppm.Vessels according to the present invention can also be manufactured witha relatively small footprint, without any moving parts, and thetechnology can be used for retrofit of existing tanks.

A detailed description of exemplary embodiments of the present inventionis given in the following. It is to be understood, however, that theinvention is not to be construed as limited to these embodiments.

Further areas of applicability will become apparent from the descriptionprovided herein. The description and specific examples in this summaryare intended for purposes of illustration only and are not intended tolimit the scope of the present disclosure.

DRAWINGS

The drawings described herein are for illustrative purposes only ofselected embodiments and not all possible implementations, and are notintended to limit the scope of the present disclosure.

In the accompanying drawings, which illustrate exemplary embodiments ofthe present invention:

FIG. 1 is a simplified perspective view of a horizontally disposed watertreatment vessel according to the present invention;

FIG. 2 a is a cut-away top plan view of a horizontally disposedembodiment according to the present invention;

FIG. 2 b is a cross-sectional view along line A-A of FIG. 2 a;

FIG. 2 c is a cross-sectional view along line B-B of FIG. 2 a;

FIG. 2 d is a cross-sectional view across a chamber of the embodiment ofFIG. 2 a;

FIG. 3 a is a detail view of weir adjustment means;

FIG. 3 b is a detail view of adjustable weirs;

FIG. 4 is a detail view of a chamber dividing wall;

FIG. 5 is a detail view of an observation port with clearing means;

FIG. 6 is a detail view of inlet weirs for use in a five-chamberhorizontal embodiment of the present invention;

FIG. 7 is a detail view of an immiscible fluid weir;

FIG. 8 a is a top plan view of a skim tank incorporating an embodimentof the present invention, comprising two horizontally disposed chambers;

FIG. 8 b is a cross-sectional view of the skim tank along line A-A ofFIG. 8 a;

FIG. 8 c is a cross-sectional view of the skim tank along line B-B ofFIG. 8 a;

FIG. 8 d is a detail view of the inlet weirs of the embodiment of FIG. 8a;

FIG. 8 e is a detail view of the immiscible fluid weir of the embodimentof FIG. 8 a;

FIG. 9 a is a top plan view of a skim tank incorporating an embodimentof the present invention, comprising four horizontally disposedchambers;

FIG. 9 b is a cross-sectional view of the skim tank along line A-A ofFIG. 9 a;

FIG. 9 c is a cross-sectional view of the skim tank along line B-B ofFIG. 9 a;

FIG. 9 d is a detail view of the inlet weirs of the embodiment of FIG. 9a;

FIG. 9 e is a detail view of the immiscible fluid weir of the embodimentof FIG. 9 a;

FIG. 10 a is a top plan view of an embodiment according to the presentinvention wherein the vessel is vertically disposed but horizontallychambered, with two cross-sectional views;

FIG. 10 b is a detail view of the inlet weirs of the embodiment of FIG.10 a;

FIG. 10 c is a detail view of the immiscible fluid weir of theembodiment of FIG. 10 a;

FIG. 11 is a flow chart illustrating a first method according to thepresent invention;

FIG. 12 is a flow chart illustrating a second method according to thepresent invention comprising steps of immiscible fluid weir adjustmentand observation port clearing;

FIG. 13 is a flow chart illustrating a third method according to thepresent invention comprising steps of selective gas bubble injection andwithholding of same;

FIG. 14 is a flow chart illustrating a fourth method according to thepresent invention involving redirection of cleaned water;

FIG. 15 is a flow chart illustrating a fifth method according to thepresent invention wherein the vessel is vertically oriented;

FIG. 16 is an illustration of a four-chambered horizontal embodimentaccording to the present invention;

FIG. 17 is a simplified top plan and elevation view of a single-chamberembodiment with a vertical orientation;

FIG. 18 is a simplified elevation view of a two-chambered embodimentwith a vertical orientation; and

FIG. 19 is a chart illustrating oil and grease concentration for variousruns.

Corresponding reference numerals indicate corresponding parts throughoutthe several views of the drawings.

DETAILED DESCRIPTION

Example embodiments will now be described more fully with reference tothe accompanying drawings.

Referring now in detail to the accompanying drawings, there areillustrated several exemplary embodiments of water treatment vesselsaccording to the present invention, each water treatment vesselgenerally referred to by the numeral 10. Referring specifically to FIG.1, a simplified perspective view of a horizontally disposed vessel 10 ispresented (this particular embodiment is rectangular in shape, althoughother shapes are possible, including some which are specificallyaddressed herein). The vessel 10 is divided into chambers 12 by means ofvertical walls 36. An injection line 14 is in fluid communication withan inlet 16 of the first chamber 12, the injection line 14 forcontaining and transmitting contaminated water (not shown) from a source(not shown). The injection line 14 receives gas bubbles (not shown;preferably microbubbles, as discussed in detail below) from bubbleinjection means 34 which are in fluid communication with the injectionline 14, allowing mixing in the injection line 14 of the gas bubbles andthe contaminated water to form an inlet fluid (not shown), which processis described in detail below. The gas bubbles can be produced by anysuitable bubble generation means, such as the apparatus and method forproducing microbubbles in liquids taught in Canadian Patent ApplicationNo. 2,460,123, mentioned above, and may comprise a mixture of gasbubbles and water (which water may be wholly or partly derived from thecleaned water produced by use of the vessel 10).

An inlet weir 18 is supported within each of the chambers 12 by firstmounting means 20 adjacent the inlet 16, while an immiscible fluid weir22 (which can be of fixed or adjustable height, as discussed below) issupported within each of the chambers by second mounting means 24, andis spaced from the inlet weir 18. The inlet weir 18 comprises a baseportion 40 and a wall portion 42, while the immiscible fluid weir alsocomprises a base portion 44 and a wall portion 46. The immiscible fluidweir 22 forms a sloped trough 26 for collecting the immiscible fluid(not shown) and allowing the immiscible fluid to flow out of thechambers through an immiscible fluid outlet 28 (which can be seen in twodifferent embodiments in FIGS. 2 a and 16) to an immiscible fluidretention tank (not shown). The immiscible fluid weir 22 is preferablycomposed of Kynar™, or polyvinylidene fluoride, a high molecular weightcrystalline thermoplastic polymer of vinylidene fluoride which haswell-known corrosion/chemical resistance properties.

When an inlet fluid is injected into the first chamber 12 (which processis described in detail below), it passes through the first inlet 16 andover the first inlet weir 18, after which the cleaned water (not shown)flows downwardly toward a cleaned water outlet 30, and a remainingmixture of the immiscible fluid and the gas bubbles floats across thefirst chamber 12 to pass over the immiscible fluid weir 22. In amulti-chamber embodiment such as that shown in FIG. 1, this partiallycleaned water is then transmitted from the cleaned water outlet 30 ofthe first chamber 12 to a second inlet 16 within the inlet weir 18 of anadjacent second chamber 12 by means of a connecting pipe 32 (which pipe32 will be sized to minimize hydraulic head, reducing friction losses toavoid substantial variations in working fluid levels in each chamber 12,as would be obvious to one skilled in the art). The connecting pipes 32are preferably composed of Schedule 10 thickness steel. Additionalbubble injection takes place by gas bubble injection means 34 on theconnecting pipe 32, introducing new bubbles to the fluid passing throughthe vessel 10 and enabling further oil/water separation in eachsubsequent chamber 12; the bubble injection in subsequent chambers 12preferably occurs near the inlet of the pipe 32, to enhance mixing timewithin the pipe 32. The immiscible fluid separated from the inlet fluidin each chamber 12 flows over and into the immiscible fluid weir 22, andthen down the trough 26 to the immiscible fluid outlet 28.

FIGS. 2 a to 2 d illustrate one embodiment of a vessel 10 according tothe present invention, specifically a horizontally disposed, cylindricalvessel 10. As was the case with the simplified illustration of FIG. 1,this embodiment comprises a series of chambers 12 separated by walls 36,each chamber 12 fluidly communicating with the next by means of aconnecting pipe 32, the first chamber 12 receiving inlet fluid via aninlet 16 (which comprises a nozzle 48). As can be seen in FIG. 2 a, thevessel 10 comprises an inlet weir 18 running along the length of thevessel 10 on one side thereof (though divided by the walls 36), and animmiscible fluid weir 22 running parallel along the opposite side of thevessel 10. Although the immiscible fluid weir 22 could be divided by thewalls 36 in some embodiments (as is the case in FIG. 16, discussedbelow), it is not divided in this embodiment but instead provides anintegrated trough 26 (as shown in FIG. 2 c) for receiving immisciblefluids from all of the chambers 12 and transmitting same towards theimmiscible fluid outlet 28. The transmission of immiscible fluids alongthe trough 26 is aided in this embodiment by heating coils 76, and anyheavy solids (not shown) or residual fluids at the end of the processcan be drained out of each chamber 12 by means of drains 78.

Each of the connecting pipes 32 is provided with gas bubble injectionmeans 34 to introduce new gas bubbles to the fluid moving from onechamber 12 to the next, as many of the gas bubbles introduced previouslywill have mixed with the immiscible fluid and passed over the immisciblefluid weir 22 rather than moving into the connecting pipe 32.

Weir adjustment means 56 may also be incorporated, and are shown in thisembodiment. As fluid levels may vary within the chambers 12 of thevessel 10 during operation, it is preferable to provide for animmiscible fluid weir 22 that is height-adjustable to preventunnecessary cleaned water loss. One embodiment of such weir adjustmentmeans 56 is illustrated in FIGS. 3 a and 3 b, described below. Where itis desired to adjust immiscible fluid weir 22 height, or simply tovisually monitor fluid levels in a closed vessel 10, observation ports58 may also be provided, as shown in FIGS. 2 a and 2 d and described indetail below with reference to FIG. 5.

In order to maintain a steady state within the vessel 10, flow controlmeans 52 are employed in this embodiment to control fluid exit at thefinal cleaned water outlet 30, and various alternative means would beobvious to anyone skilled in the art. In addition, this embodiment isprovided with recycle flow means 50 in association with the cleanedwater outlet 30, in order to utilize some of the cleaned water in abubble/water mixture for injection by the gas bubble injection means 34.The vessel 10 of FIGS. 2 a to 2 d is also provided with a gas outlet 80,as gas may collect within the gap 38 above the walls 36 in the vessel10.

FIGS. 3 a and 3 b illustrate an exemplary embodiment of weir adjustmentmeans 56 according to the present invention. As can be seen, the weiradjustment means 56 in this embodiment comprise a threaded spindle 60seated in a packing gland 62 (shown in FIG. 3 a), which threaded spindle60 connects to the immiscible fluid weir 22 (shown in FIG. 3 b). As thespindle 60 is rotated, it moves up and down (depending on direction ofrotation), converting rotational motion to linear motion and therebymoving the immiscible fluid weir 22 up or down accordingly in response.Other means for adjusting the weir 22 height would be obvious to oneskilled in the art. By adjusting the weir 22 height to address fluidvolume conditions in a given chamber 12 (as the weir 22 can be dividedby the walls 36 to form discrete weirs 22 for each chamber 12), a usercan limit the amount of cleaned water that is escaping over the wallportion 46 of the immiscible fluid weir 22, raising the weir 22 when thewater/oil froth interface level is high and lowering it when theinterface level is low.

FIG. 4 illustrates an exemplary embodiment of a chamber-dividing wall36, including cut-outs to receive an immiscible fluid weir 22 and allowpassage of a connecting pipe 32 therethrough.

FIG. 5 illustrates an exemplary embodiment of an observation port 58with observation port clearing means 72. In cases where the watertreatment vessel 10 is closed, observation ports 58 provide means tovisually inspect the state of the vessel 10 contents, and specificallythe fluid levels therein (which would, for example, enable appropriateadjustment to the immiscible fluid weir 22 height by weir adjustmentmeans 56). The vessel 10 is provided with an aperture 64 in an uppersurface thereof, in which is seated a nozzle fitting 66. The nozzlefitting 66 is capped by a tempered glass viewing pane 68, which pane 68is held in place by a retention member 70. It is necessary to providefor a properly sealed observation port 58 where the vessel 10 is apressure vessel, however, sealing of the observation ports 58 may alsohave utility in other contexts, such as for preventing leakage duringflow surges. The observation ports 58 may also be provided withobservation port clearing means 72, as shown in FIG. 5; such means 72 inthis exemplary embodiment comprise a conduit 74, which conduit 74 could,for example, be used to enable a steady injection of a small amount ofgas to prevent vapour accumulation in the observation port 58, oralternatively to enable selective injection of warm water to keep thepane 68 clear. Other means for enabling vessel 10 content monitoringwould be obvious to one skilled in the art, as would means formaintaining the functionality of the monitoring means.

FIGS. 6 and 7 show one embodiment of inlet weirs 18 and an immisciblefluid weir 22 for use in a five-chamber horizontal, cylindrical vessel10. It can be seen in FIG. 6 that the wall portion 42 of the inlet weirs18 is angled away from the point at which the base portion 40 would beattached to the vessel 10 at the first mounting means 20. Due to thecylindrical shape of the vessel 10, the inlet weirs 18 for the first andfifth chambers 12 would have a curved edge to mate with the innerchamber 12 surface, and the inlet weirs 18 for all chambers 12 but thefirst would be provided with means to receive a connecting pipe 32. Inthis embodiment of the immiscible fluid weir 22, as seen in FIG. 7, thebase 44 and wall 46 portions of the weir 22 have curved edges whereappropriate for mating with the vessel 10 inner surfaces.

FIGS. 8 a to 8 e illustrate another embodiment of a vessel 10 accordingto the present invention, specifically a two-chamber, horizontallydisposed vessel 10 with an API or “skim tank” configuration. As was thecase with the embodiments of FIGS. 1 and 2 a, the vessel 10 is dividedinto chambers 12 by a vertical wall 36, the chambers 12 in fluidcommunication via a connecting pipe 32, gas bubble injection means 34introduce gas bubbles into the connecting pipe 32, and inlet weirs 18and an immiscible fluid weir 22 are disposed opposite to each otheracross the chamber 12 with the immiscible fluid weir 22 in fluidcommunication with the immiscible fluid outlet 28. However, unlike theembodiments of FIGS. 1 and 2 a, this embodiment comprises two inletweirs 18 mounted on opposite sides of the vessel 10, with the immisciblefluid weir 22 centrally mounted within the vessel 10 and extendingdiametrically across the interior, situated above the dividing wall 36.The immiscible fluid weir 22 still forms a trough 26 (as can be seen inFIGS. 8 c and 8 e), with heating coils 76, but that trough 26 receives amixture of immiscible fluid and gas bubbles simultaneously from twodirections—a first mixture is received from the first chamber 12(labelled “Chamber #1”), and when cleaned water from the first chamber12 flows through the connecting pipe 32 to the second chamber 12(labelled “Chamber #2”) it is mixed with gas bubbles to form an inletfluid that will separate in the second chamber 12 to produce abubble/immiscible fluid mixture that will flow into the immiscible fluidweir 22 from the second chamber 12. Again, the inlet weirs 18 comprise awall portion 42 that is angled away from the vessel 10 inner surface,and the inlet weirs 18 and immiscible fluid weir 22 have curved edges toenable proper mating with the vessel 10 inner surface.

FIGS. 9 a to 9 e illustrate yet another embodiment of the presentinvention, specifically a four-chamber, horizontally disposed vessel 10with an API or “skim tank” configuration. The structure is very similarto that of the embodiment of FIGS. 8 a to 8 e, sharing many elements,and there is no difference in terms of the immiscible fluid weir 22 andrelated components. However, this embodiment is provided with additionalwalls 36 to divide the vessel 10 interior into four chambers 12 ofgenerally equal volume. Accordingly, the vessel 10 is provided withadditional connecting pipes 32 (with gas bubble injection means 34, asshown in FIG. 9 d) to allow for fluid communication between the fourchambers 12 (the first chamber 12 connecting to the second chamber 12,the second chamber 12 to the third, etc.), and the inlet weirs 18 onopposed sides of the vessel 10 are divided roughly in half by the walls36 to form a total of four discrete inlet weirs 18.

FIGS. 10 a to 10 c illustrate yet another embodiment of the presentinvention, this time a four-chamber, vertically disposed vessel 10. Aswas the case with the embodiment of FIGS. 9 a to 9 e, with which thisembodiment shares many features, the vessel 10 interior is divided intofour chambers 12 of generally equal volume by walls 36 which extendupwardly from the bottom of the vessel 10 to the immiscible fluid weir22, leaving a gap 38 above the immiscible fluid weir 22. The walls 36again divide the opposed inlet weirs 18 roughly in half, resulting infour discrete inlet weirs 18, all in fluid connection in series by meansof connecting pipes 32 (with gas bubble injection means 34) at inlets16.

FIG. 16 illustrates yet another embodiment of the present invention, arectangular, four-chamber, horizontally disposed vessel 10. Thisembodiment employs a lid 82 for removably sealing the vessel 10, and adifferent immiscible fluid weir 22 arrangement than in the embodimentsdiscussed above. In this embodiment, there are four chambers 12 dividedby walls 36, in fluid communication by means of connecting pipes 32, butthe walls 36 divide not only the inlet weirs 18 but also the immisciblefluid weir 22, resulting in four discrete immiscible fluid weirs 22.Each of the discrete immiscible fluid weirs 22, therefore, has acorresponding immiscible fluid outlet 28 which would be provided with anozzle to allow flow to a common outlet header (not shown) for drainage.In this embodiment, the inlets 16 for the inlet weirs 18 are providedwith globe valves 54 to control the flow of microbubbles into thechambers 12.

Another vertically disposed vessel 10 configuration is illustrated inFIG. 17. In this embodiment, the vessel 10 has only a single chamber 12.The injection line 14, with associated gas bubble injection means 34,extends across the vessel 10 interior to a generally central locationwithin the chamber 12; the injection line 14 may be contained within arigid pipe or supported by a rib extending from the vessel 10 innersurface, which would be the first mounting means 20, although othersupport/mounting means are possible within the scope of the presentinvention and would be obvious to one skilled in the art. The injectionline 14 is in fluid communication with an inlet 16, which inlet 16allows for introduction of inlet fluid into the centrally disposed inletweir 18. A peripherally disposed immiscible fluid weir 22 is mountedaround the inner surface of the vessel 10, with an immiscible fluidoutlet 28 in fluid communication therewith.

A two-chambered embodiment of a vertically disposed vessel 10configuration is illustrated in FIG. 18. In this embodiment, the vessel10 has two chambers 12 separated by a wall 36. The inlet 16 allowsinjection of contaminated water (which has been mixed with microbubbles,not shown) against and over the inlet weir 18 in the uppermost chamber12, with the mixture of microbubbles and immiscible fluid floatingacross the uppermost chamber 12, passing over the immiscible fluid weir22, and flowing out of the immiscible fluid outlet 28. The remainingfluid passes downwardly toward an inlet of the connecting pipe 32, andthence past gas bubble injection means 34 where additional gas bubblesare mixed with the fluid before the fluid moves into the lowermostchamber 12. Upon entering the lowermost chamber 12, the fluid flowsagainst and over the inlet weir 18, the bubble/immiscible fluid againmoving across the chamber 12 to pass over the immiscible fluid weir 22and out the immiscible fluid outlet 28. The remaining cleaned water thenflows out the cleaned water outlet 30. This embodiment is also providedwith an observation port 58, a gas outlet 80, flow control means 52, anda drain 78, as described in detail above with respect to similarembodiments.

The present invention also comprises various methods for separatingwater and immiscible fluids. FIGS. 11 to 15 illustrate methods, or partsof methods, according to the present invention.

Referring now to FIG. 11, which sets out a basic method according to thepresent invention for cleaning contaminated water, the first step (at100) is to provide a water treatment vessel comprising at least onechamber, an inlet weir supported within the at least one chamber byfirst mounting means, and an immiscible fluid weir supported within theat least one chamber by second mounting means, spaced from the inletweir. The vessel is sized to provide sufficient residence time as percustomer specifications, which residence times are typically 10 minutes.The next step (at 102) is to transmit the contaminated water from itssource toward that chamber via an injection line. Contaminated waterentering the vessel is usually produced water received from primaryseparation units such as a “Free Water Knockout” (FWKO) unit or“treater”. The composition of this produced water varies considerablybetween sites and contents can fluctuate largely depending on the sites'operations. Typical oil and grease concentrations vary between 50 ppmand 2000 ppm, and oil properties (including density and viscosity) varyby site. Oil can be found in an emulsified form, as either a reverseemulsion or a normal emulsion, and certain clarifier chemicals may beadded to aid in the flotation, on top of those chemicals that arealready added to the system for normal operations. Total suspendedsolids and trace chemical compounds (such as sulphur and iron compounds)concentrations are also site specific. Water inlet temperature can varyfrom 20° C. to 90° C. In some methods according to the presentinvention, clean water could also be introduced into the vessel beforeinjection of the contaminated water.

Bubble generation means are provided for generating bubbles at 104, andthe bubbles are generated and injected into the injection line at 106.Bubble generation means may include those taught in Canadian PatentApplication No. 2,460,123, mentioned above, where gas experiences shear,impact and pressure resulting in bubbles 5 to 50 microns in diameter.Smaller bubbles more effectively separate oil from water, resulting in adrier froth and low skim volume. The bubbles are then allowed to mixwith the contaminated water in the injection line, forming an inletfluid at 108. The bubbles are being used before separation ever takesplace, the intent being to form a mixture, unlike some competitiveseparation technologies which generate/inject bubbles to directly andimmediately cause separation of oil out of the water. As shown in FIG.16, globe valves 54 can be positioned adjacent the inlets 16 to controlthe inlet fluid injection; the globe valves 54 can also be used tocreate a pressure drop. The inlet fluid is reduced in pressure acrossthe globe valves 54, with the result that some of the dissolved gas isreleased from solution and forms bubbles; some of the bubbles that arealready in the inlet fluid grow with this pressure reduction and an areaof turbulence is set up at the injection point that encourages thebubbles to contact the oil and also causes the gas bubbles to coalesceand enhance the flotation in the vessel 10.

The inlet fluid is then injected at 110 into the chamber at an inletadjacent the inlet weir, and the inlet fluid is allowed to pass over theinlet weir at 112. Separation of water and immiscible fluid then occursat 114, with the cleaned water being allowed to flow downwardly underforce of gravity to a cleaned water outlet at 116 and this cleaned wateris drained off at 118. The remaining mixture of immiscible fluid and gasbubbles is then allowed to float across the chamber and over theimmiscible fluid weir at 120, and the immiscible fluid is finallyallowed to collect in a trough and flow out an immiscible fluid outletat 122. The drawing of fluid from the last chamber results in a pressuredrop that drives the system; the water flows through the system bygravity and hence there is a hydraulic gradient through the vessel, soany connecting pipes (as described below with respect to FIG. 13) arepreferably sized to minimize the pressure drop.

Referring now to FIG. 12, steps relating to immiscible fluid weir heightadjustment, observation ports and clearing means are illustrated, whichare preferably but not necessarily part of a method according to thepresent invention. As there is a hydraulic gradient through the vessel,and the interconnecting pipe is therefore sized to minimize the pressuredrop, there will usually be a slight difference in level in eachchamber. This difference in level means that the oil weirs have to beadjustable to minimize water loss with the oil. After step 100 set outabove, a step 124 can be included whereby the vessel is provided withimmiscible fluid weir height adjustment means, at least one observationport, and observation port clearing means. The method can thenincorporate the step (at 126) of observing the fluid level in thechamber by means of the observation port, to enable adjusting theimmiscible fluid weir height adjustment means to minimize cleaned waterloss over the immiscible fluid weir. The immiscible fluid weir heightadjustment means can then be adjusted at 128 to minimize cleaned waterloss over the immiscible fluid weir, and gas or water can be injectedinto the observation port at 130 to clear the port of any build-up. Itwill be appreciated by persons skilled in the art that there would notbe a sharp separation between the frothy immiscible fluid and thecleaned water, which fact would be taken into account when establishingan appropriate immiscible fluid weir height.

In methods where the vessel is provided with at least two chambers, theat least two chambers in fluid communication by means of at least oneconnecting pipe, which is shown at step 132 of FIG. 13, the methodpreferably comprises allowing the cleaned water at 134 to pass from thebottom of a first of the at least two chambers to a point adjacent theinlet weir of an adjacent second of the at least two chambers by meansof the at least one connecting pipe. At step 136, gas bubbles are thenselectively injected at a location in the at least one connecting pipespaced from the inlet weir of the adjacent second of the at least twochambers, and gas bubble injection is withheld at step 138 in the atleast one connecting pipe leading into a last of the at least twochambers, thereby forming a calming zone. Provision is preferably madefor the addition of bubbles between the next-to-last and last chambersso that they can be added if there is a sudden surge in the inlet oilconcentration which cannot be adequately handled by the first chambers.While testing of vessels according to the present invention hasconfirmed that as much as 90% of the oil can be removed from the inletfluid in the first chamber alone, additional chambers have proven usefulin removing additional amounts of contaminant.

FIG. 14 illustrates another optional step, where after step 118 (shownin FIG. 11) a step 140 may be undertaken whereby at least a portion ofthe cleaned water from the cleaned water outlet is redirected to thebubble generation means. Approximately half of the recycle flow ispreferably redirected to the bubble generation means for mixing with thecontaminated water. The bubbles and entrained oil are therefore inintimate contact upon entering the vessel, and this mixed flow entersthe inlet and overflows the inlet weir into the first chamber.

FIG. 15 illustrates steps relating to vertically oriented vessels suchas that illustrated in FIG. 17. In such a case, and after step 100, theinlet weir is centrally disposed within the at least one chamber at 142,and the immiscible fluid weir at 144 is circumferentially disposed aboutthe inner surface of the at least one chamber, the immiscible fluid weirbeing spaced from and disposed generally above the inlet weir.

Referring again to the embodiment of FIGS. 8 a to 8 e, the vessel 10would be sized to allow for sufficient residence time, usually between60 and 120 minutes depending on customer specifications, but withadditional volume to allow for surge capacity. To preventshort-circuiting of bubbles and oil through the system, downwardvelocity of fluid flow through each chamber 12 is preferably maintainedbelow 1.4 ft/min. In a method incorporating a vessel 10 in accordancewith the embodiment of FIGS. 9 a to 9 e or FIG. 17, residence times aretypically kept at approximately 10 minutes, with appropriate downwardvelocities being maintained, as would be appreciated and understood bysomeone skilled in the art.

Test Results

A test vessel was manufactured on the same configuration as thatillustrated in FIG. 16. The test vessel had the followingcharacteristics:

Volume (total)=1.4 m³

Volume (1^(st) chamber)=0.39 m³

Volume (2^(nd) chamber)=0.31 m³

Volume (3^(rd) chamber)=0.35 m³

Volume (4^(th) chamber)=0.35 m³

The working volume was approximately 85% of the capacities listed above,and therefore:

Working volume (total)=1.2 m³

Working volume (1^(st) chamber)=0.33 m³

Working volume (2^(nd) chamber)=0.26 m³

Working volume (3^(rd) chamber)=0.30 m³

Working volume (4^(th) chamber)=0.30 m³

The diameter of the interconnecting piping was 3 inches.

The run conditions were as follows:

The microbubbles were created using bubble generation means inaccordance with Canadian Patent Application No. 2,460,123, mentionedabove.

Flow rate through the bubble generation means=5 usgpm

Produced water flow rate=10 gpm

Back pressure on the bubble generation means=60 psi

Pressure of gas to the bubble generation means=110 psi

Water temperature=62 degrees C.

The test runs were conducted using a method according to the presentinvention.

The results of the test runs are set out in Table 1 (below) and FIG. 19.Note that “MBF” refers to a microbubble flotation unit.

Produce:

TABLE 1 Sample Location Oil and Grease (mg/L) MBF In 263 MBF Out 6 MBFIn 257 MBF Out 4 MBF In 441 MBF Out 10 MBF In 427 MBF Out 12 MBF In 279MBF Out 7 MBF In 332 MBF Out 5 MBF In 271 MBF Out 14 MBF In 318 MBF Out15

As can readily be seen from the test results, a vessel and methodaccording to the present invention was highly effective in removingimmiscible fluid content from contaminated water. The vessel required aminimal retention period, removed oil droplets less than 50 microns indiameter, and could handle solids, flow rate fluctuations, and oilconcentrations of greater than 300 ppm. The vessel also had a relativelysmall footprint, without any moving parts, and it would be clear topersons skilled in the art that the technology can be used for retrofitof existing tanks.

While particular embodiments of the present invention have beendescribed in the foregoing, it is to be understood that otherembodiments are possible within the scope of the invention and areintended to be included herein. It will be clear to any person skilledin the art that modifications of and adjustments to this invention, notshown, are possible without departing from the spirit of the inventionas demonstrated through the exemplary embodiments. The invention istherefore to be considered limited solely by the scope of the appendedclaims.

The foregoing description of the embodiments has been provided forpurposes of illustration and description. It is not intended to beexhaustive or to limit the disclosure. Individual elements or featuresof a particular embodiment are generally not limited to that particularembodiment, but, where applicable, are interchangeable and can be usedin a selected embodiment, even if not specifically shown or described.The same may also be varied in many ways. Such variations are not to beregarded as a departure from the disclosure, and all such modificationsare intended to be included within the scope of the disclosure.

1. A method for removing immiscible fluid from contaminated water from asource, the method comprising the steps of: (a) providing a watertreatment vessel comprising at least one chamber, an inlet weirsupported within the at least one chamber by first mounting means, andan immiscible fluid weir supported within the at least one chamber bysecond mounting means, spaced from the inlet weir; (b) transmitting thecontaminated water from the source toward the at least one chamber bymeans of an injection line; (c) providing bubble generation means forgenerating bubbles; (d) generating and injecting the bubbles into theinjection line; (e) allowing the bubbles and contaminated water to mixin the injection line to form an inlet fluid; (f) injecting the inletfluid into the at least one chamber at an inlet adjacent the inlet weir;(g) allowing the inlet fluid to pass over the inlet weir; (h) allowingcleaned water and a remaining mixture of immiscible fluid and gasbubbles to separate from each other; (i) allowing the cleaned water toflow downwardly by gravity to a cleaned water outlet; (j) draining offthe cleaned water through the cleaned water outlet; (k) allowing theremaining mixture of immiscible fluid and gas bubbles to float acrossthe at least one chamber and over the immiscible fluid weir; and (l)allowing the immiscible fluid to collect in a trough within the at leastone chamber and flow out an immiscible fluid outlet.
 2. The method ofclaim 1 further comprising: a step after step (a) but before step (b) ofproviding the water treatment vessel with immiscible fluid weir heightadjustment means; and a step before step (k) of adjusting the immisciblefluid weir height adjustment means to minimize cleaned water loss overthe immiscible fluid weir.
 3. The method of claim 2 further comprising:a step after step (a) but before step (b) of providing the watertreatment vessel with at least one observation port; and a step beforestep (k) of observing fluid level in the at least one chamber by meansof the at least one observation port, to enable adjusting the immisciblefluid weir height adjustment means to minimize cleaned water loss overthe immiscible fluid weir.
 4. The method of claim 3 further comprising:a step after step (a) but before step (b) of providing the watertreatment vessel with observation port clearing means; and a step ofinjecting gas or water into the observation port to clear theobservation port of any build-up.
 5. The method of claim 1 wherein thewater treatment vessel is provided with at least two chambers, the atleast two chambers in fluid communication by means of at least oneconnecting pipe, the method further comprising the step after step (i)of allowing the cleaned water to pass from the bottom of a first of theat least two chambers to a point adjacent the inlet weir of an adjacentsecond of the at least two chambers by means of the at least oneconnecting pipe.
 6. The method of claim 1 wherein the bubble generationmeans generate microbubbles.
 7. The method of claim 1 wherein thebubbles are composed of a gas selected from the group consisting of air,hydrocarbon gas, and nitrogen.
 8. The method of claim 1 furthercomprising a step after step (j) of redirecting at least a portion ofthe cleaned water from the cleaned water outlet to the bubble generationmeans.
 9. The method of claim 8 wherein approximately half of thecleaned water from the cleaned water outlet is redirected to the bubblegeneration means.
 10. The method of claim 5 further comprising a step ofselectively injecting gas bubbles at a location in the at least oneconnecting pipe spaced from the inlet weir of the adjacent second of theat least two chambers.
 11. The method of claim 10 further comprising astep of withholding gas bubble injection in the at least one connectingpipe leading into a last of the at least two chambers, thereby forming acalming zone.
 12. The method of claim 1 further comprising: a step ofproviding the water treatment vessel with flow control means on thecleaned water outlet; and a step of using the flow control means tomaintain volume of fluid exiting the cleaned water outlet substantiallyequal to volume of the inlet fluid entering the water treatment vessel,allowing for a steady state within the water treatment vessel.
 13. Themethod of claim 1 further comprising: a step of disposing the watertreatment vessel in a vertical orientation; a step of centrallydisposing the inlet weir within the at least one chamber; and a step ofcircumferentially disposing the immiscible fluid weir about the innersurface of the at least one chamber, the immiscible fluid weir beingspaced from and disposed generally above the inlet weir.
 14. The methodof claim 1 further comprising a step after step (l) of collecting theimmiscible fluid in an immiscible fluid retention tank.